Rules of Chess - 2

Some advance level Rules

Castling
Once in every game, each king is allowed to make a special move, known as castling. Castling consists of moving the king two squares along the first rank toward a rook (which is on the player's first rank[note 1] ) and then placing the rook on the last square the king has just crossed. Castling is permissible only if all of the following conditions hold:[2]


 * Neither of the pieces involved in castling may have been previously moved during the game.
 * There must be no pieces between the king and the rook.
 * The king may not be in check, nor may the king pass through squares that are under attack by enemy pieces, nor move to a square where it is in check.

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En Passant
Once in every game, each king is allowed to make a special move, known as castling. Castling consists of moving the king two squares along the first rank toward a rook (which is on the player's first rank[note 1] ) and then placing the rook on the last square the king has just crossed. Castling is permissible only if all of the following conditions hold:[2]


 * Neither of the pieces involved in castling may have been previously moved during the game.
 * There must be no pieces between the king and the rook.
 * The king may not be in check, nor may the king pass through squares that are under attack by enemy pieces, nor move to a square where it is in check.

Promotion
When a pawn advances to the eighth rank, as a part of the move it is  promoted and must be exchanged for the player's choice of queen, rook, bishop, or knight of the same color. Usually, the pawn is chosen to be promoted to a queen, but in some cases another piece is chosen; this is called underpromotion. In the diagram on the right, the pawn on c7 can be advanced to the eighth rank and be promoted to an allowed piece. There is no restriction placed on the piece that is chosen on promotion, so it is possible to have more pieces of the same type than at the start of the game (for example, two queens).

Check and Check Mate
When a king is under immediate attack by one or two of the opponent's pieces, it is said to be in  check. A response to a check is a legal move if it results in a position where the king is no longer under direct attack (that is, not in check). This can involve capturing the checking piece; interposing a piece between the checking piece and the king (which is possible only if the attacking piece is a queen, rook, or bishop and there is a square between it and the king); or moving the king to a square where it is not under attack. Castling is not a permissible response to a check. The object of the game is to checkmate the opponent; this occurs when the opponent's king is in check, and there is no legal way to remove it from attack. It is illegal for a player to make a move that would put or leave his own king in check.